The present invention relates in general to semiconductors, and more particularly to integrated imaging circuits.
High resolution imaging systems such as scanners and digital cameras capture images by projecting light from an object through a lens and onto an optical sensor. A low manufacturing cost and low power operation is achieved by fabricating the sensor on a semiconductor die configured with an array of photoactive sensing devices such as charge-coupled devices, photodiodes, or phototransistors. The photoactive devices respond to the light projected from the object by generating proportional pixel signals which are processed through an imaging circuit to produce viewable imaging data.
In most imaging systems, different regions of the sensor have different responses to the light projected from the image. That is, photoactive devices in different regions of the sensor generate pixel signals of different amplitudes even when the light intensity is the same. Such nonuniformities can be caused by semiconductor process variations across the die, aberrations in a focusing lens or by thermal gradients across the sensor. As a result, objectionable shadows are present in portions of the displayed image.
Hence, there is a need for an improved imaging system that can compensate for different responses to light across different regions of an optical sensor.